This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. We are continuing our studies on the structure and mechanism of molecular chaperone proteins which, broadly speaking, facilitate the correct folding, assembly and targeting of proteins and RNA molecules in cells. Systems that are currently under study include a "prokaryotic proteasome"?a 850 kDa complex that is a simple homolog of the eukaryotic proteasome;a chaperone that facilitates folding and assembly of membrane proteins in bacteria;and a family of RNA chaperones/helicases that modulate RNA structure in cells. Combined with other biophysical studies, we are now examining substrate recognition properties of many of these proteins by characterizing target peptides or RNAs and co-crystallizing complexes for structure determination.